The invention is directed to the air flow systems in automobiles and in particular to the treated air flow systems in automobiles such as defrosters, air conditioning and heating systems.
In automobile systems, the defrost system and the air conditioning system as well as the heating system typically are all contained under the dashboard and prior art efforts to use standard (feedback) type fluidic nozzles while, basically, functionally good in sweeping a jet of air across the windshield, the physical size required by the fluidic element is much too large to fit within the dash, particularly in small and downsized automobiles. For example, the outlet of some automobiles ducting is about 3.times.5 inches. If one were to use the smaller 3" dimension for the power nozzle width (W) of the fluidic element, the resultant length of the nozzle would be too long. Experiments with the resultant sweeping air jet from such a large element to discover more about its uniformity characteristics in the air showed that the frequency standard of the oscillator is in the order of 10 H.sub.z and at an air velocity of about 100 feet per second, the characteristic wavelength is in the order of about 10 feet which is satisfactory.
The operational basis for the oscillating jet is that a concentrated jet would be uniformly swept over the windshield so that the intensity of the heat, because of minimal mixing with ambient, would be maximized at the point of impact of the air stream but would be uniformly distributed by the sweeping action. In order to accomplish this, the sweeping rate or frequency of the air stream must be low enough compared to the velocity of the air jets so that the wavelength is long compared to the nozzle. When the wavelength is long, a small portion of the stream resides in the ambient air before impacting the windshield. On the other hand, with a short wavelength much of the stream resides in the ambient air, producing severe mixing with the ambient, which for defrost purposes tends to defeat the purpose at hand. However, for air conditioning purposes, a low sweeping rate is desired in the initial cool down phase of the air confined within the automobile and the, after the vehicle has been cooled down, a mixing with the ambient is desired so as to maintain the temperature. This dual sweep frequency concept is also desirable for the heating of the vehicle that is to say, the initial heating is obtained by a low rate or frequency of sweeping of the air stream in the passenger compartment in order to more rapidly cool down or heat up the passenger compartment and then, after a short time interval the sweep rate is increased to thereby produce mixing of the freshly cooled or heated air with the air in the passenger compartment.
In order to satisfy the requirement of small space and to minimize ambient mixing for defrost operation which is undesirable since it lowers the thermal energy of air impacting the windshield, the present invention provides an oscillator whose frequency is independent of the air stream properties and whose frequency is characteristically low. However, the invention also provides an oscillator whose frequency can be changed dependant upon time and/or temperature to achieve an initial low frequency of operation so as to assure a rapid heating and/or cooling of the passenger compartment and subsequently, a higher frequency of oscillation to assure a better mixing characteristic (in contrast to the defrost operation) after the passenger compartment has been cooled or heated for a selected period of time.
The present invention provides a vibrating reed air stream oscillator, preferably constituted by a thin resilient reed in the shape of an inverted "T" which is supported in cantelevered fashion from the stem of the "T" in the duct. This provides an air initiated oscillation mechanism which is extremely reliable, very low in last cost and can be installed or incorporated in existing defrost systems without significant structural modification and which does not require any additional space and, in fact, can reduce the space requirements since it results in a much more efficient and rapid defrost of an automobile windshield by concentrating the heated air rather than diffusing it over a wide or long path. That is to say, intstead of a diffuser of wide angles, the air stream is swept over the wide angle and, in some cases, a single defrost air outlet adjacent to the windshield can accommodate the entire windshield.